Diesel vehicles, and some gasoline fueled vehicles, generally include an exhaust particulate filter to reduce emissions of solid particles that are products of fuel combustion. Some regulations, such as US EPA and California Air Resources Board (CARB), require that these filters be diagnosed for leaks. One solution to this diagnostics problem is an electrostatic particulate matter (PM) sensor that detects the amount of soot and other solid particles in vehicle exhaust. This sensor generally relies on a pair of parallel electrodes separated by an air gap with a voltage across the electrodes to detect particulate matter (PM). Because the soot that enters the sensor with exhaust gas is usually charged (for example, about 33% positive charge and 33% negative charge), a portion of the soot will typically deposit on the sensor electrodes. As more particles accumulate on each electrode, they may form dendritic structures perpendicular to the electrode surface. Charge tends to pool at the tip of the dendrites as they grow and, eventually, they may become long enough that the electrostatic force attracting the particles to the opposing electrode exceeds the force holding the dendrite together and to the electrode wall. Once the force holding the dendrite is exceeded, it may break off and carry its pooled charge to the opposite electrode. This charge transfer may be measured as a current between the electrodes. The rate at which break-off and charge transfer occurs may be roughly proportional to the rate at which soot is entering the sensor.